A flow-rate measurement device including a measurement flow channel unit stored in a fluid flow channel unit has been known as a conventional flow-rate measurement device. For example, in a flow-rate measurement device disclosed in PTL 1, a measurement flow channel unit around which a rubber band is wound is stored in a gas flow channel unit, and a flow rate sensor is disposed at the side face of the measurement flow channel unit. With this rubber band, the gap between the inner surface of the gas flow channel unit and the outer surface of the measurement flow channel unit is closed. Thus, gas in the gas flow channel unit is guided to the measurement flow channel unit, and the flow rate of the gas flowing through the measurement flow channel unit is measured with the flow rate sensor.
However, in the conventional flow-rate measurement device disclosed in PTL 1, the flow rate sensor is disposed away from an electric circuit that measures the flow rate, and thus, a long lead line for connecting the flow rate sensor and the electric circuit is needed. Consequently, external noise is likely to enter the lead line, entailing deterioration in the measurement precision due to noise.